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Epilobium hirsutum seed head dispersing seeds. In spermatophyte plants, seed dispersal is the movement, spread or transport of seeds away from the parent plant. [1] Plants have limited mobility and rely upon a variety of dispersal vectors to transport their seeds, including both abiotic vectors, such as the wind, and living vectors such as birds.
Plants are limited by vegetative reproduction and consequently rely upon a variety of dispersal vectors to transport their propagules, including both abiotic and biotic vectors. Seeds can be dispersed away from the parent plant individually or collectively, as well as dispersed in both space and time.
Phloem (/ ˈ f l oʊ. əm /, FLOH-əm) is the living tissue in vascular plants that transports the soluble organic compounds made during photosynthesis and known as photosynthates, in particular the sugar sucrose, [1] to the rest of the plant. This transport process is called translocation. [2]
Plant ABCB transporters have shown to transport the phytohormone indole-3-acetic acid ( IAA), [69] also known as auxin, the essential regulator for plant growth and development. [ 70 ] [ 71 ] The directional polar transport of auxin mediates plant environmental responses through processes such as phototropism and gravitropism. [ 72 ]
An intermediate type of loading exists that uses symplastic transport but utilizes a size-exclusion mechanism to ensure diffusion is a one-way process between the mesophyll and phloem cells. This process is referred to as polymer-trapping, in which simple solutes such as sucrose are synthesized into larger molecules such as stachyose or ...
In plants, sucrose transport is distributed throughout the plant by the proton-pump where the pump, as discussed above, creates a gradient of protons so that there are many more on one side of the membrane than the other. As the protons diffuse back across the membrane, the free energy liberated by this diffusion is used to co-transport sucrose ...
As water transport mechanisms, and waterproof cuticles, evolved, plants could survive without being continually covered by a film of water. This transition from poikilohydry to homoiohydry opened up new potential for colonization. [33] Plants then needed a robust internal structure that held long narrow channels for transporting water from the ...
Some plants appear not to load phloem by active transport. In these cases, a mechanism known as the polymer trap mechanism was proposed by Robert Turgeon. [5] In this model, small sugars such as sucrose move into intermediary cells through narrow plasmodesmata, where they are polymerised to raffinose and other larger oligosaccharides. As larger ...